In order to piece together weather data from before this time, scientists analyse sediment cores taken from ocean and lake floors and from frozen ice cores .
Ice cores are cylinders of ice drilled out of an ice sheet or glacier.
As layers of fresh snow fall and sediment becomes buried, they trap and preserve (store) evidence of the global temperature experienced at that time of the burial. Investigating the physical and chemical make-up of the ice core can tell us of past changes in climate.
Most ice core records come from Antarctica and Greenland. The oldest continuous ice core records are from Greenland and go back 130,000 years.
Greenland Ice Sheet
Alternating light and dark bands storing evidence of past climates.
Antarctic Ice Sheet
1. The location of ice sheets used for evidence of past changes in climate
Light and dark bands alternate like tree rings in this ice core from Greenland. The longest ice cores can be more than 3 km deep.
Go to YouTube and look up ‘National Ice Core Lab Stores Valuable Ancient Ice – Science Nation’ (2:32) to see how ice cores are extracted and stored.
Each silver tube on these shelves contains a 1-metre-long section of an ice core. They are stored at a temperature of –36 °C.
236
FUN FACT! Ireland’s climate is
changing in line with global
patterns. By the middle of this century (2041–2060) the average annual
temperatures are projected to increase by between 1–1.2 °C and 1.3–1.6 °C.